* plugin/dns64: update readme and owners

Make @superq code owner of the plugins. Update the readme a bit:

* don't make it start with a quote
* make it look more like other README's in syntax description
* make a full corefile examples and tests these by setting the corefile
  language tag
Signed-off-by: Miek Gieben <miek@miek.nl>

* Update plugin/dns64/README.md
Co-Authored-By: Ben Kochie <superq@gmail.com>

* Update plugin/dns64/README.md
Co-Authored-By: Ben Kochie <superq@gmail.com>

* Update plugin/dns64/README.md
Co-Authored-By: Ben Kochie <superq@gmail.com>

* Update plugin/dns64/README.md
Co-Authored-By: Ben Kochie <superq@gmail.com>

* Update plugin/dns64/README.md
Co-Authored-By: Ben Kochie <superq@gmail.com>
Co-authored-by: Ben Kochie <superq@gmail.com>